1. Field of the Invention
This invention relates generally to semiconductor manufacturing, and, more particularly, to a method and apparatus for performing process lifetime tracking of trench feature using optical analysis.
2. Description of the Related Art
The technology explosion in the manufacturing industry has resulted in many new and innovative manufacturing processes. Today""s manufacturing processes, particularly semiconductor manufacturing processes, call for a large number of important steps. These process steps are usually vital, and therefore, require a number of inputs that are generally fine-tuned to maintain proper manufacturing control.
The manufacture of semiconductor devices requires a number of discrete process steps to create a packaged semiconductor device from raw semiconductor material. The various processes, from the initial growth of the semiconductor material, the slicing of the semiconductor crystal into individual wafers, the fabrication stages (etching, doping, ion implanting, or the like), to the packaging and final testing of the completed device, are so different from one another and specialized that the processes may be performed in different manufacturing locations that contain different control schemes.
Generally, a set of processing steps is performed on a group of semiconductor wafers, sometimes referred to as a lot, using a semiconductor manufacturing tool called an exposure tool or a stepper. Typically, an etch process is then performed on the semiconductor wafers to shape objects on the semiconductor wafer, each of which may function as a gate electrode for a transistor. Typically, shallow trench isolation (STI) structures formed on the semiconductor wafers being processed are filled by forming silicon oxide using tetraethoxysilane to (TEOS), over the STI structures. The manufacturing tools communicate with a manufacturing framework or a network of processing modules. Each manufacturing tool is generally connected to an equipment interface. The equipment interface is connected to a machine interface to which a manufacturing network is connected, thereby facilitating communications between the manufacturing tool and the manufacturing framework. The machine interface can generally be part of an advanced process control (APC) system. The APC system initiates a control script, which can be a software program that automatically retrieves the data needed to execute a manufacturing process.
FIG. 1 illustrates a typical semiconductor wafer 105. The wafer 105 typically includes a plurality of individual semiconductor die arranged in a grid 150. Photolithography steps are typically performed by a stepper on approximately one to four die locations at a time, depending on the specific photomask employed. Photolithography steps are generally performed to form patterned layers of photoresist above one or more process layers that are to be patterned. The patterned photoresist layer can be used as a mask during etching processes, wet or dry, performed on the underlying layer or layers of material, e.g., a layer of polysilicon, metal or insulating material, to transfer the desired pattern to the underlying layer. The patterned layer of photoresist is comprised of a plurality of features, e.g., line-type features, such as a polysilicon line, or opening-type features, that are to be replicated in an underlying process layer.
Turning now to FIG. 2, a silicon substrate 210 that contains at least one layer (layer 220), is shown. In one embodiment, a layer of silicon nitrite is added onto a surface 215 of the silicon substrate 210, producing the layer 220. Typically, a plurality of STI structures 240 are etched into the silicon substrate 210. Generally, rounding of the corners can occur during the production of the STI structures 240. Currently, prolifilometer and scanning electron microscopes (SEM) are used to calculate and measure an inline depth 250, a profile of the STI structures 240, and the like. However, these measurements can contain inaccuracies, which may cause errors during semiconductor wafer manufacturing processes.
Turning now to FIG. 3, a pre-polished layer of TEOS fill material, which is represented by layer 230, is shown deposited on the silicon substrate 210. Upon deposition of the TEOS material onto the silicon substrate 210 and the layer 220, one or more seams 310 may develop above the STI structures 240. In addition to the seams 310, one or more keyholes 320 may develop within the STI structures 240. The keyholes 320 can cause significant weaknesses, leakage problems, and other errors to occur in the semiconductor wafer. Current methods of detecting seams 310 and keyholes 320 generally require inefficient interruption of process flow and/or destructive testing of sample semiconductor wafers 105.
Turning now to FIG. 4, a silicon substrate 210 that has been subjected to a post TEOS polish process and a silicon nitride layer strip process, is illustrated. The STI structures 240 are left with a field oxide 410 filling within the STI structures 240. In one embodiment the field oxide comprises a silicon oxide material deposited using TEOS. The integrity of the field oxide 410, may be compromised by the existence of keyholes 320. Again, the detection of keyholes requires inefficient interruption of the manufacturing process flows and/or destructive testing to examine cross-sections of the STI structures 240.
The present invention is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.
In one aspect of the present invention, a method is provided for performing process lifetime tracking of trench features. A plurality of process steps is performed on a first set of semiconductor wafers. A manufacturing lifetime tracking of trench features is performed. A feedback corrective process is performed on a second set of semiconductor wafers based upon the lifetime tracking trench features. A feed-forward corrective process is performed on the first set of semiconductor wafers based upon the manufacturing lifetime tracking of trench features.
In another aspect of the present invention, a system is provided for performing process lifetime tracking of trench features. The system of the present invention comprises: a computer system; a manufacturing model coupled with the computer system, the manufacturing model being capable of generating and modifying at least one control input parameter signal; a machine interface coupled with the manufacturing model, the machine interface being capable of receiving process recipes from the manufacturing model; a processing tool capable of processing semiconductor wafers and coupled with the machine interface, the first processing tool being capable of receiving at least one control input parameter signal from the machine interface; a metrology tool coupled with the first processing tool and the second processing tool, the metrology tool being capable of acquiring metrology data; an optical data reference library, the scatterometry reference library comprising optical data related to a plurality trench data; and an optical data error analysis unit coupled to the metrology tool and the optical data reference library, the optical data error analysis unit capable of comparing the metrology data to corresponding data in the optical data reference library and performing a process lifetime tracking of trench features.